Preparation of magnetic nitrogen-doped porous carbon by incomplete combustion with solvothermal synthesis for magnetic solid-phase extraction of benzoylurea insecticides from environmental water

Abstract

In this work, magnetic nitrogen-doped porous carbon (Fe₃O₄@N-PC) was prepared via incomplete combustion coupled with solvothermal synthesis for extraction of four benzoylureas (BUs) insecticides. Among them, nitrogen-doped porous carbon was produced through incomplete combustion of filter paper loaded with mixture formed by Zn(NO₃)₂·6H₂O and polyethyleneimine solution, and magnetic nanoparticles were further introduced by solvothermal method. Compared with magnetic porous carbon (Fe₃O₄@PC), the surface hydrophilicity of Fe₃O₄@N-PC was improved by virtue of the doping of nitrogen atoms, and the dispersion of Fe₃O₄ was more uniform, which greatly exposed the adsorption site. The characterization of Fe₃O₄@N-PC were carried out by TEM, XRD, elemental analysis, XPS, BET and magnetic hysteresis curve. Besides, Fe₃O₄@N-PC was successfully used as magnetic solid-phase extraction (MSPE) adsorbent, which showed excellent enrichment factors and extraction recoveries toward polar BUs insecticides due to the polar surface and introduction of Lewis-basic nitrogen. The optimum amount of Fe₃O₄@N-PC adsorbent, extraction time, pH value, desorption solvent, desorption time and PEI concentration for BUs insecticides extraction were determined to be 3 mg, 10 min, 8, acetone/acetic acid (19:1, V/V), 6 min and 60 g L^-1, respectively. Under this experimental condition, the enrichment factors ranged from 182 to 192 with good intra- and inter-day relative standard deviations (RSDs). The calibration lines were linear over the concentration in the range of 1-800 μg L^-1, the limit of detection (LOD) and limit of quantification (LOQ) were 0.3 μg L^-1 as well as 1 μg L^-1, respectively. The recoveries for spiked sample ranged from 90.7 to 107.3% in spiked Yellow River water with the RSDs less than 7.0%. The results showed that the established MSPE strategy based on Fe₃O₄@N-PC could be used for the detection of trace BUs in complex samples.

Keywords: Benzoylurea insecticides; Environmental water; High performance liquid chromatography; Magnetic solid-phase extraction; Nitrogen-doped porous carbon.